f2fs: throttle the memory footprint with a sysfs entry

This patch introduces ram_thresh, a sysfs entry, which controls the memory
footprint used by the free nid list and the nat cache.

Previously, the free nid list was controlled by MAX_FREE_NIDS, while the nat
cache was managed by NM_WOUT_THRESHOLD.
However, this approach cannot be applied dynamically according to the system.

So, this patch adds ram_thresh that users can specify the threshold, which is
in order of 1 / 1024.
For example, if the total ram size is 4GB and the value is set to 10 by default,
f2fs tries to control the number of free nids and nat caches not to consume over
10 * (4GB / 1024) = 10MB.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 20 insertions, 3 deletions

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index d27e65a1fb0b..fec4967fb8d2 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -26,6 +26,22 @@
 static struct kmem_cache *nat_entry_slab;
 static struct kmem_cache *free_nid_slab;
 
+static inline bool available_free_memory(struct f2fs_nm_info *nm_i, int type)
+{
+        struct sysinfo val;
+        unsigned long mem_size = 0;
+
+        si_meminfo(&val);
+        if (type == FREE_NIDS)
+                mem_size = nm_i->fcnt * sizeof(struct free_nid);
+        else if (type == NAT_ENTRIES)
+                mem_size += nm_i->nat_cnt * sizeof(struct nat_entry);
+        mem_size >>= 12;
+
+        /* give 50:50 memory for free nids and nat caches respectively */
+        return (mem_size < ((val.totalram * nm_i->ram_thresh) >> 11));
+}
+
 static void clear_node_page_dirty(struct page *page)
 {
         struct address_space *mapping = page->mapping;
@@ -208,7 +224,7 @@ int try_to_free_nats(struct f2fs_sb_info *sbi, int nr_shrink)
 {
         struct f2fs_nm_info *nm_i = NM_I(sbi);
 
-        if (nm_i->nat_cnt <= NM_WOUT_THRESHOLD || nr_shrink <= 0)
+        if (available_free_memory(nm_i, NAT_ENTRIES) || nr_shrink <= 0)
                 return 0;
 
         write_lock(&nm_i->nat_tree_lock);
@@ -1288,7 +1304,7 @@ static int add_free_nid(struct f2fs_nm_info *nm_i, nid_t nid, bool build)
         struct nat_entry *ne;
         bool allocated = false;
 
-        if (nm_i->fcnt > 2 * MAX_FREE_NIDS)
+        if (!available_free_memory(nm_i, FREE_NIDS))
                 return -1;
 
         /* 0 nid should not be used */
@@ -1473,7 +1489,7 @@ void alloc_nid_failed(struct f2fs_sb_info *sbi, nid_t nid)
         spin_lock(&nm_i->free_nid_list_lock);
         i = __lookup_free_nid_list(nm_i, nid);
         f2fs_bug_on(!i || i->state != NID_ALLOC);
-        if (nm_i->fcnt > 2 * MAX_FREE_NIDS) {
+        if (!available_free_memory(nm_i, FREE_NIDS)) {
                 __del_from_free_nid_list(nm_i, i);
         } else {
                 i->state = NID_NEW;
@@ -1836,6 +1852,7 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
         nm_i->max_nid = NAT_ENTRY_PER_BLOCK * nat_blocks - 3;
         nm_i->fcnt = 0;
         nm_i->nat_cnt = 0;
+        nm_i->ram_thresh = DEF_RAM_THRESHOLD;
 
         INIT_RADIX_TREE(&nm_i->free_nid_root, GFP_ATOMIC);
         INIT_LIST_HEAD(&nm_i->free_nid_list);